ios - 无法在 iOS Swift 中获取 SecKey UnsafeMutablePointer

Question

我在swift中做一个涉及RSA加密的项目，遇到一个指针问题如下:

我有一个全局 var publicKey: SecKey?可选值，我需要获取 UnsafeMutablePointer<Unmanaged<SecKey>?>指向它的指针，即 SecKeyGeneratePair 中所需的数据类型功能。

我试图将指针定义为:

var keyPointer = UnsafeMutablePointer<Unmanaged<SecKey>?>(publicKey!)

但是编译器提示Cannot invoke 'init' with an argument of type @lvalue SecKey错误

根据 Using Swift with Cocoa and Objective-C 一书，在 Core Foundation 和 Unmanaged Objects 部分，它指出Unmanaged<T>结构提供了2个方法takeUnretainedValue()和 takeRetainedValue() .但尝试实现它们时，会出现以下错误

var keyPointer = UnsafeMutablePointer<Unmanaged<SecKey>?>(publicKey!.takeRetainedValue())

“SecKey”没有名为“takeRetainedValue”的成员

任何解决此问题的帮助将不胜感激

Answer 1

试试这个:

var publicKey: SecKey?
var privateKey: SecKey?

var publicKeyUnManaged:Unmanaged<SecKey>?
var privateKeyUnManaged:Unmanaged<SecKey>?
let dic:[String:String] = [kSecAttrKeyType:kSecAttrKeyTypeRSA, kSecAttrKeySizeInBits:"2048"]
SecKeyGeneratePair(dic, &publicKeyUnManaged, &privateKeyUnManaged)

publicKey = publicKeyUnManaged?.takeRetainedValue()
privateKey = privateKeyUnManaged?.takeRetainedValue()

您不必创建 UnsafeMutablePointer<Unmanaged<SecKey>?>手动。如 this document 中所述,

When a function is declared as taking an UnsafeMutablePointer argument, it can accept any of the following:

• nil, which is passed as a null pointer
• An UnsafeMutablePointer value
• An in-out expression whose operand is a stored lvalue of type Type, which is passed as the address of the lvalue
• An in-out [Type] value, which is passed as a pointer to the start of the array, and lifetime-extended for the duration of the call

在这种情况下，我们可以使用第三个“in-out”表达式。